Sure, whomever that is very determined to invest in bitcoin will not think of establishing a reliable source of income at that initial stage when they want to start their investment but they can buy with any amount they can invest in without being affected by other demands.
Are you even listening to yourself? Where would he/she get the discretionary income to invest into Bitcoin in the first place without a reliable source of income? Let's say for example, such a person win a lottery or somehow managed to get some money and invested it into Bitcoin, fine. What is the possibility of continuity of such investment without a reliable source of income? It even being able to build your backup funds?
I'll be quick to remind you that starting your Bitcoin accumulation journey isn't the major challenge, but sustaining it and I don't know how the investor can do that without a reliable source of income. A good income source is very important for the investor to be able to take care of his expenses and make discretionary income available to continue investing into Bitcoin and be able to build various variations of backup funds like emergency fund and others.
One can decide to seek for a concrete source of income later on and by then, they are already hodlers. Wanting to affirm a stable source of income prior to investing in bitcoin will only result to either delay in time of accumulation or missing out an opportunity to acquire bitcoin at cheaper prices.
This pattern lacks planning and by the time the investor is seeking such concrete source of income, needs and expenses might have started weighing them down and they'll have no other option than to start liquidating their Bitcoin holdings in order to survive. A good source of income is always very necessary prior to your investing into Bitcoin for the sustainability of such investment.
That's right, someone who invests in bitcoin must be able to increase their income, so that the investor has more cold cash to be able to invest more in bitcoin. However, increasing your income is not as easy as you imagine, because extra hard work is needed to achieve this. Especially for bitcoin investors who have office jobs where it is very difficult to get a salary increase, in my opinion it is more difficult for these investors to increase their income. Because of course these investors don't have much time to develop their innovations, because they spend a lot of time working in the office. Therefore, the solution for people like this may be to simply save and not have to buy something if it is not necessary. And besides, even if a bitcoin investor cannot increase his income. I don't think this will be a barrier to continuing to invest in bitcoin. Because the important thing is that the money invested is cold money, even if the nominal value is small. So basically this (being able to increase income) when investing in bitcoin, may not be mandatory, because in reality not everyone can do it.
There's always provisions to upgrade oneself in any career unless the person involved is lazy minded. Every career has growth opportunities and you must not stay on your job forever, if you're very good in what you do, you might have a better offer somewhere else and you go for it, instantly your salary is increased and you can be more aggressive in your accumulation.
Optionally, the investor can take up part time jobs to service his investment only and use his salary to service his expenses. It's all about determination and proper planning. We can achieve whatever we desire.